Alcohols are a renewable and clean fuel source. A grain alcohol commonly used as a fuel source is ethanol, which can be produced, in large part, from corn by the fermentation of starch. Generally, ethanol production is accomplished through a fermentation and distillation process wherein starches are released and converted to sugars, and then the sugars are converted to alcohol by the addition of yeast. At an industrial level, yeast fermentation processes only convert about one-third of the corn into ethanol.
Ethanol production facilities often begin the production process with a dry or wet milling process. In dry milling, corn, or another suitable grain, is ground up by a hammer or roller mill into a dry mixture of particles. The dry mixture of particles is combined with water and enzymes to break up the starch from the corn into smaller fragments and then subject the smaller fragments to a saccharification phase wherein the starch is converted to sugar. After the saccharification phase, resulting sugars are fermented with yeast to facilitate their conversion to ethanol.
Ethanol yield is dependent upon initial starch content of the corn as well as the availability of the starch to the enzymes that are used in the saccharification phase. In conventional processes, the availability of starch is governed, in part, by the success of the dry milling or similar step in which the corn is broken up into smaller particles. Production processes currently used in commercial ethanol plants are not able to achieve maximum theoretical ethanol yield, thus more corn than theoretically needed must be used to produce a certain amount of ethanol.
In an attempt to increase ethanol yield, cavitation has been used; however, it has been limited to reducing particle size of the feed material for the purposes of enhancing subsequent treatment and providing more surface area for enzymatic breakdown of the starches to take place. Additionally, to achieve good particle size reduction, cavitational forces apply aggressive, shear stresses to the grain particles. If the cavitational forces apply too aggressive a shear force in terms of intensity, energy and/or duration, it is possible to cause damage to the components being treated. For example, a significant decrease in the particle size could have an adverse affect on downstream processing steps.
Also, aggressive cavitational forces can degrade desirable proteins and inactivate the enzymes. By collapsing hydrodynamic cavitation bubbles formed under specific conditions, extremely high local pressures and temperatures can be generated, which can promote enzyme denaturation. Cavitation can also promote chemical reactions involving H. and OH. free radicals formed by decomposing water inside the collapsing hydrodynamic cavitation bubbles. These free radicals could be scavenged by some amino acid residues of the enzymes participating in structure stability, substrate binding, or catalytic functions.
Accordingly, there is still a need for a process that can obtain a closer to theoretical maximum yield.